The Lunar Orbiter Laser Altimeter (LOLA) is one of seven instruments aboard the Lunar
Reconnaissance Orbiter (LRO) spacecraft with the objectives to determine the global
topography of the lunar surface at high resolution, measure landing site slopes and search
for polar ices in shadowed regions. The LOLA laser transmitter is a passively Q-switched
crossed-Porro resonator. All components used in the laser have space flight heritage. The
flight laser bench houses two oscillators (a primary and a cold spare) that are designed to
operate sequentially during the mission. If the primary laser can no longer provide
adequate scientific data products, the secondary laser will be turned on. The baseline
mission calls for LOLA (and LRO) to spend about one year studying the Moon. Since
LOLA operates at 28 Hz, the laser system needs to produce approximately one billion
pulses during the primary one year mission. To validate that the LOLA laser design is
capable of meeting this requirement, the LOLA Engineering Model (EM) laser has been
subjected to extended operation testing in vacuum. In this paper we will summarize the
longevity validation test effort of the LOLA EM laser.